﻿using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;

namespace WebInstaller
{
    public class CSVHelper
    {
        /// <summary>
        /// 将DataTable中数据写入到CSV文件中
        /// </summary>
        /// <param name="dt">提供保存数据的DataTable</param>
        /// <param name="fileName">CSV的文件路径</param>
        public static void SaveCSV(DataTable dt, string fullPath)
        {
            FileInfo fi = new FileInfo(fullPath);
            if (!fi.Directory.Exists)
            {
                fi.Directory.Create();
            }
            FileStream fs = new FileStream(fullPath, System.IO.FileMode.Create, System.IO.FileAccess.Write);
            //StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.UTF8);
            string data = "";
            //写出列名称
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                data += dt.Columns[i].ColumnName.ToString();
                if (i < dt.Columns.Count - 1)
                {
                    data += ",";
                }
            }
            sw.WriteLine(data);
            //写出各行数据
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                data = "";
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    string str = dt.Rows[i][j].ToString();
                    str = str.Replace("\"", "\"\"");//替换英文冒号 英文冒号需要换成两个冒号
                    if (str.Contains(',') || str.Contains('"')
                        || str.Contains('\r') || str.Contains('\n')) //含逗号 冒号 换行符的需要放到引号中
                    {
                        str = string.Format("\"{0}\"", str);
                    }

                    data += str;
                    if (j < dt.Columns.Count - 1)
                    {
                        data += ",";
                    }
                }
                sw.WriteLine(data);
            }
            sw.Close();
            fs.Close();
        }

        /// <summary>
        /// 将CSV文件的数据读取到DataTable中
        /// </summary>
        /// <param name="fileName">CSV文件路径</param>
        /// <returns>返回读取了CSV数据的DataTable</returns>
        public static DataTable OpenCSV(string filePath)
        {
            try
            {
                DataTable dt = new DataTable();
                FileStream fs = new FileStream(filePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);

                StreamReader sr = new StreamReader(fs, System.Text.Encoding.Default);
                //记录每次读取的一行记录
                string strLine = "";
                //记录每行记录中的各字段内容
                string[] aryLine = null;
                string[] tableHead = null;
                //标示列数
                int columnCount = 0;
                //标示是否是读取的第一行
                bool IsFirst = true;
                //逐行读取CSV中的数据
                while ((strLine = sr.ReadLine()) != null)
                {
                    if (IsFirst == true)
                    {
                        tableHead = strLine.Split(',');
                        IsFirst = false;
                        columnCount = tableHead.Length;
                        //创建列
                        for (int i = 0; i < columnCount; i++)
                        {
                            DataColumn dc = new DataColumn(tableHead[i]);
                            dt.Columns.Add(dc);
                        }
                    }
                    else
                    {
                        aryLine = strLine.Split(',');
                        DataRow dr = dt.NewRow();
                        for (int j = 0; j < columnCount; j++)
                        {
                            dr[j] = aryLine[j];
                        }
                        dt.Rows.Add(dr);
                    }
                }
                //if (aryLine != null && aryLine.Length > 0)
                //{
                //    dt.DefaultView.Sort = tableHead[0] + " " + "asc";
                //}
                sr.Close();
                fs.Close();
                return dt;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        public static Encoding GetFileEncoding(string filePath)
        {
            Encoding Result = null;
            FileInfo info = new FileInfo(filePath);
            FileStream fs = default(FileStream);
            try
            {
                fs = info.OpenRead();
                Encoding[] unicodeEncodings =
                {
                   Encoding.BigEndianUnicode,
                   Encoding.Unicode,
                   Encoding.UTF8,
                   Encoding.UTF32,
                   Encoding.UTF7,
                   new UTF32Encoding(true,true)
               };
                for (int i = 0; Result == null && i < unicodeEncodings.Length; i++)
                {
                    fs.Position = 0;
                    byte[] preamble = unicodeEncodings[i].GetPreamble();
                    bool isEqual = true;
                    for (int j = 0; isEqual && j < preamble.Length; j++)
                    {
                        isEqual = preamble[j] == fs.ReadByte();
                    }
                    if (isEqual)
                        Result = unicodeEncodings[i];

                }
            }
            catch (IOException ex)
            {
                throw ex;
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();//包括了Dispose,并通过GC强行释放资源
                }
            }
            if (object.ReferenceEquals(null, Result))
            {
                Result = Encoding.Default;
            }
            return Result;
        }

    }
}
